Lubricating compositions



United States latent Ofifice Patented June 15, 1%65 This invention relates to lubricants, particularly those useful for lubrication under severe operating conditions, such as those under extreme high speed and at high temperatures and to a new and novel class of compounds therefor.

It is well known that the high pressure occurring in certain types of gears and bearings may cause rupture of lubricant films with consequent damageto the machinery. proved in their protective properties for rubbing surfaces by the addition of certain substances, so-called extreme pressure agents, so that excessive wear, scuifing and seizure which normally follow a break in the film lubricant are minimized or prevented.

It is known that certain compounds of metal-reactive elements, such as certain compounds of chlorine, sulfur and phosphorus, as well as certain other compounds, such as some compounds of lead, impart extreme pressure properties to various lubricants. Notable among the substances heretofore used are the lead soaps, phosphoric acid esters, free or bound sulfurand certain chlorinated organic compounds. A principal objection to many of these extreme pressure agents is their generally high re-' activity with the metallic surface, causing etching, corrosion and discoloration of the metal surface. Another objection to chemically reactive extreme pressure agents is that they alter the original chemical nature of the contacting surface, which under certain conditions is undesirable. Additionally, because of the activity of agents of this type, they usually are depleted rapidly resulting in only a temporary solution to the problem of extreme pressure lubrication.

It has now been discovered that improved extreme pressure lubricants are provided by a suitable lubricating oil containing an oil-soluble polythioether-ester-ether derivative obtained by reacting (a) an ester of a long chain unsaturated fatty acid, RCOOH, and a polyoxyalkylene diol or its thio derivative having the formula where R and R" are the same or different alkyl radicals of from 2 to 8, preferably 2 to 3 carbon atoms, X is oxygen or sulfur and x and y are integers of at least 1,

7 preferably 1 to 6 with (b) a mercapto compound such as a mercapto acid, alcohol, ether or ester'so that the end product has at least 1 and preferably z thioether radi- It is known that various base lubricants can be imurated fatty acid ester of the polyoxyalkylene glycol may be represented by the corresponding formula and the thioether thereof by the formula The intermediate ether-esters are prepared by esterifying a long chain unsaturated fatty acid such as oleic acid, linoleic acid, linolenic acid, erucic acid, ricinoleic acid and the like with a polyoxyalkylene diol or the thio derivatves thereof, such as diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, dibutylene glycol, 2,2'-thiodiethanol, 3,3- thiodipropanol, and. the like. Esters of these materials include diethylene glycol dioleate, triethylene dioleate, dipropylene glycol dioleate, diethylene glycol linoleate, tetraethylene glycol n'cinoleate, dibutylene glycol oleate, 2,2'-thiodiethanol dioleate, 2,2-thiodiethanol diricinoleate, 2,2-thiodiethanol linoleate and the like.

Compounds of the present invention are prepared by reacting the ether-ester with a mercapto compound such as mercapto aliphatic carboxylic acids, e.g., mercaptoacetic acid, mercaptopropionic acid, mercaptobutyric acid, or mercapto-alkanols such as Z-mercaptoethanol, 2- and 3-mercaptopropanol, 2-, 3- and 4-mercaptobutanol or ethers of said mercaptoalcohols such as methyl or octyl 2- mercaptoethanyl or mercapto esters, e.g., ethyl mercaptoacetate or ethyl mercaptobutyrate, and mixtures thereof.

The additives can be prepared by the methods described by Koenig et al., JACS, 79,-362 (1957), or Fitzgerald, Jr., Org. Chem., 22, 197 (1957), and preferably 'at low temperatures, from room temperature to about 50 C., in the presence of a free radical catalyst such as azo or peroxide catalysts or ultraviolet light and a non-reactive solvent such as benzene, toluene, xylene, or the like. Suitable initiators include various free radical-yielding, heterocyclic and alicyclic peroxides, such as diethyl peroxide, tertiary butyl hydroperoxide, dibenzoyl peroxide, ditertbutyl peroxide, dimethylthienyl peroxide, dicyclohexyl peroxide, dilauroyl peroxide and urea peroxide. These are mentioned by way of non-limiting examples of suitable organic peroxides. Other initiating compounds known include emulsion redox systems, such as a mixture of sodium bisulfite and persulfate, ammonium persulfate, alkali metal perborates azo compounds, such as alpha,alpha-azodiisobutyronitrile, etc.

The following examples illustrate the preparation of suitable additives for use in accordance with the present invention.

EXAMPLE I About .600 grams of diethylene glycol dioleate and 223.5 grams of mercaptoacetic acid were mixed in a flask at 2025 C. About 240 drops (30 drops at a time) of t-butyl hydroperoxide were added over a period of 2 hours 7 and the temperature was kept at about 37 C. The reac- 3 EXAMPLETII About 600 grams of triethylene glycol dioleate and 223.5 grams of mercaptoacetic acid were mixed in a flask at 20-25 C. About 240 (30 drops at a time) of t-butyl hydroperoxide were added over a period of 2 hours and the temperature was kept at about 37 C. The reaction mixture was diluted with 2 volumes of diethyl ether, washed with 12 liters of Water to pH 4, dried over Na SO filtered and the solvent stripped at 155 C. and 2 mm. pressure. The final product was a mixture'of the 9- and 10-carboxymethylmercaptostearate diesters of triethylene glycol. V I g EXAMPLE III and the temperature was kept at about 37 C. The reaction mixture was diluted with 2 olumes of diethyl ether, washed with 12 liters of water to. pH 4, dried over Na- SO filtered and the solvent strippedaat 155 C. and 2 pressure. The final product was a mixture of the 9- and 10-carboxymethylmercapto 12 hydroxylstearate diester .of diethylene glycol.

About 600 grams 'of diethylene glycol dioleate and 223.5 grams of mercaptoethanol were mixed in a flask at 7 20-25 C. About 240 drops (30 drops at a time) of A (SAE (B) (SAE 10w 7 30) Vascosity, SUS at 44 58 Viscosity index 90 -60 Other suitable oils are the gas turbine lube oils having the following properties:

t-butyl hydroperoxide were added over a period of 2 hours and the temperature was kept at about 37 C; The reaction mixture was diluted with 2 volumes of diethyl ether,

washed with 12 liters of water to pH 4, dried over Na SO filtered and the solvent'stripped at 155 C. and 12 mm. pressure. The final product was a mixture of diethylene glycol di(9- and 10-['2-hydroxyethylmercapto]-stearate).

' EXAMPLE v About 600 grams of 2,2' thiodiethanol dioleate and 223.5 gramsof mercaptoacetic acid were mixed ina flask at 20-25 C. About 240 drops drops at a time) of t-butyl hydroperoxide were added over a period of 2 hours and the temperature was keptat about 37 C. The reaction mixture was diluted With 2 volumesof diethyl ether, 'washed with 12; liters of water to pHV4, dried over Na SO filtered and the solvent stripped at 155 C. and 2mm pressure, The final product was a mixture of 2,2-thiodiethanol di(9- and 10 carboxymethylmercaptostearate).

The mercapto-modified polyether-esters are oil-soluble and can be used in amounts of from about 0.5% to about 7 20%, preferably from about 1% to about 5% by weight.

Lubricating oils useful-for the preparation of compositions of this invention can be one or more of a variety of synthetic oils or natural hydrocarbon oils having a vis- 'e'osity range of from so. SUS at 100 B10250 SUS at f 210 -F.'(SAE viscosity number ranging from SAE 10W to SAE 90). The natural hydrocarbon oils can be obtained from paratfinic naphthenic, iasphaltic or mixed base crudes, and/ or mixtures thereof refined as by extraction a-cid treat ment clay treatment; Synthetic oils include polymerized olefins, alkylated .aromatics ispmerized waxes, co'polyy mers of alkylene glycjols and alkylene oxide (Ucon fluids) which are described in US. Patents 2,425,755, 2,425,845

V and 2,774,733 such as Ucon 50HB170 Ucon 50HB660 or Ucon LB550X and which are copolyrner-s of ethylene and '1,2-pr opylene oxides,;the'monoand diols, as well as their ether derivatives; organic esters of aliphatic dibasic' acids such asdi-2-ethylhexyl sebacate or di-Z-ethylhexyl adipate and the like. The hydrocarbon oils may be blended with fixed oils such as castor oil, lard oil. and the like and/or synthetic oils as mentioned .or silicone polymers and the like. Typical oils of this type include petroleum motor 1010 mineral oil Essentially balance. 7 Composition C V V Example III. additive 2% A a 1010 mineral oil Essentially balance.

Composition Example IV additive 2%. '1010 mineral oil Essentially balance.

Composition E A Example IIadditive 1%.- V 5 SAE30 mineral oil Essentially balance.

2 Composition F lExample V additive 2%. a SAE 90 mineral oil Essentially balance.

Cornposition G Example I additive 2%. Lauric acid 2%. V g a SAE 90 mineral oil Essentially balance;

j Composition H 7 7 Example I additive 5%. Ucon 50HB660 (polyethylene-proj pylene glycol having'a SUS at 100 F. of 660) a Essentially balance. I

7 Composition I I Example I'additive' 2%. Di-2 ethylhexyl sebacate Essentially balance.

Composition A Example I additive 2%.

1010 mineral oil a Essentiallybalance.

Composition B Example n additive 2%.

l Compositions of this -inyention were evaluated for their 7 extreme pressure properties. on .a spuregear machine}.

The machine consists essentially of two 'geometricallysiniilar pairs of gears connected by'two parallelshafts; The gear pairs are placed in separate gear boxes, which also contain the-supporting ball bearings; ()ne of the; shafts' consists-of-two sectionsconnected by-a couplingr: Loading is accomplished by looking one side of the coupling and applying torque. to the other. Theliconditions of a the test-were: b f A' Speed i A "2pm"; 3200' Oil temperature C .100

Oil fiow-rajte cc./se;;;; 10 :Load in increments '5 min. at each setting.

A, B, C and B through I. 10,000-l2,000. 1010 minenal oil+2% C alkenyl succinic acid 1,400 (3,200 rpm).

1010 mineral oil+2% malonic acid 2,800. 1010 mineral oil+2% 3-hexadecyl ad-ipic acid 1,400. 1010 mineral oi=l+2% dode- 'cyl-mercaptosnccinic acid 1,400. 1010 mineral oi1+l0% glycerol monooleate 1,800.

1010 mineral oil+2% C13H27 OH (OXO process) 600. 1010 mineral oil 600.

The data show the outstanding enhancement of the load-carrying ability of the oil effected by the mercaptocontaining compounds of the invention, as represented by those of Compositions A through I. On the other hand, malonic acid, succinic acid, 3-hexadecy-1 adipic acid and C -alkenyl succinic acid as well as sulfur-containing acids outside the scope used by applicant such as dodecylmercapto-succinic acid, or other types of esters and alcohols such as glycerol-monooleate, lauric acid or OX alcohol effected only a slight improvement.

Compositions of the present invention were also tested for their corrosion and sludge resistant properties by the following methods: (1}a Timken 2126 steel bearing was immersed in a test composition and placed in an open air over at 150 C. for 65 hours, and at the end of the test, the bearing examined and (2) steel rods (3/16" by 3") were immersed in test compositions for 21 /2 hours at 150 C. and the amount of sludge formed on the rods was noted as shown in Table 11.

TABLE 11 Composition 1 2 Composition A No stain 0.7 mg. sludge. 1010 Mineral oil 2% 3(z2-ethyl- Badly staiued- 60 mg. sludge.

hexyDadipie acid. 1010 Mineral oil 2% 9- and 10- carboxystearic acid.

100 mg. sludge.

having 18 carbon atoms and a diol selected from the group consisting of polyethylene glycol and 2,v2'-thiodiethanol, the :thioether radical components of the ester being represented by s CH -z 1.. where Z is a polar radical selected fi'om the group represented by O and COO and R is selected from the group consisting of hydrogen and C alky1r-adical and n is an integer of from 1 to 4.

A mineral lubricating oil composition comprising a major amount of mineral lubricating oil and from about 1% to about 5% of an oil-soluble dicarboxy C alkyl mercapto stearate diester of polyethylene glycol.

.3. A mineral lubricating oil composition comprising a major amount of mineral lubricating oil and from about 1% to about 5% of an oil-soluble dicarboxy C alkyl mercapto hydroxystearate diester of polyethylene glycol.

4. A mineral lubricating oil composition comprising a major amount of mineral lubricating oil and from about 1% to about 5% of di(canboxy-C alkyl mercapto) containing 2,2'-thicdiethanol dioleate.

5. A mineral lubricating oil composition comprising a major amount of mineral lubricating oil and from about 1% to about 5% of dicarboxymethylmercaptostearate diester of diethylene glycol.

6. A mineral lubricating oil composition comprising a major amount of mineral lubricating oil and from about 1% to about 5% of di(carboxymethylmercapto) containing 2,2'thiodiethanol dioleate.

7. A mineral lubricating oil composition comprising a major amount of mineral lubricating oil and from about 1% to about 5% of a mixture of 9- and 10-carboxymethylmercaptostearate diester of diethylene glycol.

8. A mineral lubricating oil composition comprising a major amount of mineral lubricating oil and from about 1% to about 5% 2,2'-thiodiethanol di(9- and 10-carboxymethylmercaptostearate) References Cited by the Examiner UNITED STATES PATENTS 2,073,841 3/37 Humphreys et a1 25248.6 2,318,629 5/43 Prutton 25248.6 X 2,454,568 11/48 Pollock 260-39 9 2,476,129 7/ 49 Augustine 260399 2,540,570 Q/51 Cyphers 25248.6 2,649,416 8/53 Richter et a1. 25248.6 2,994,662 -8/ 61 Calhoun et a1 25248.6 3,041,283 6/62 Calhoun et a1. 25248.6 3,041,284 6/ 62 Calhoun et a1 25248.6

FOREIGN PATENTS 520,034 12/55 Canada. 657,750 9/51 Great Britain.

DANIEL E. WYNIAN, Primary Examiner.

JULIUS GREENWALD, JOSEPH R. LIBERMAN, Examiners. 

1. A MINERAL LUBRICATING OIL COMPOSITION COMPRISING A MAJOR AMOUNT OF MINERAL LUBRICATING OIL AND FROM ABOUT 0.5% TO ABOUT 20% OF AN OIL-SOLUBLE DITHAIETHER DERIVATIVE OF A DIESTER OF A LONG CHAIN UNSATURATED FATTY ACID HAVING 18 CARBON ATOMS AND A DIOL SELECTED FROM THE GROUP CONSISTING OF POLYETHYLENE GLYCOL AND 2,2''-THIODIETHANOL, THE THIOETHER RADICAL COMPONENTS OF THE ESTER BEING REPRESENTED BY 